我正在尝试使用Parsec编写类似csv的解析器。 到现在为止还挺好。 解析器解码标头，并处理一切正常。 现在，我试图在文件开头跳过一些注释。 注释以# （或空行）开头。 如果这样做， endBy循环不会在标头启动时出现，而是会失败。
这是我的代码：
csvParser = do
-- skipping comment bit
P.endBy ((P.char '#' >> P.many (P.noneOf "\n"))
<|> P.many P.space
) eol
-- real parsing starting
header <- parseHeader
eol
case header of
["style", "number", "quantity", "length", "width", "height"] -> parsePL
otherwise -> error $ "Can't decore following header:" ++ (show header)
where parseHeader = P.sepBy cell sep
sep = P.char ','
eol = P.char '\n'
cell = P.many (P.noneOf ",\n")
cellp = do x <- cell ; sep; return x
today = "2015/01/15" :: Date
readR :: String -> Rational
readR x = toRational x' where
x' = read x :: Float
parsePL = P.endBy (do
style <- cellp
numberOfBox <- read <$> cellp
numberPerBox <- cellp
length <- readR <$> cellp
width <- readR <$> cellp
height <- readR <$> cell
return (style, numberOfBox, length, width, height, "", 0, "", today)
) eol
